U.S. patent application number 09/930010 was filed with the patent office on 2002-02-14 for composition for ceramic substrate and ceramic circuit component.
This patent application is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to Kishida, Kazuo, Shiratori, Akira, Takagi, Hiroshi, Yokokura, Osamu.
Application Number | 20020019304 09/930010 |
Document ID | / |
Family ID | 15719359 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020019304 |
Kind Code |
A1 |
Kishida, Kazuo ; et
al. |
February 14, 2002 |
Composition for ceramic substrate and ceramic circuit component
Abstract
There is disclosed a composition for a ceramic substrate
comprising a mixture of: powdered borosilicate-based glass
comprising about 5% to 17.5% by weight of B.sub.2O.sub.3, about 28%
to 44% by weight of SiO.sub.2, 0% to about 20% by weight of
Al.sub.2O.sub.3, and about 36% to 50% by weight of MO (where MO is
at least one selected from the group consisting of CaO, MgO, and
BaO), and a powdered ceramic; in which the amount of the powdered
borosilicate-based glass is about 40% to 49% by weight based on the
total amount of the composition for a ceramic substrate, and the
amount of the powdered ceramic is about 60% to 51% by weight based
on the total amount of the composition for a ceramic substrate.
Inventors: |
Kishida, Kazuo; (Yasu-gun,
JP) ; Shiratori, Akira; (Yasu-gun, JP) ;
Yokokura, Osamu; (Omihachiman-shi, JP) ; Takagi,
Hiroshi; (Otsu-shi, JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
|
Assignee: |
Murata Manufacturing Co.,
Ltd.
|
Family ID: |
15719359 |
Appl. No.: |
09/930010 |
Filed: |
August 15, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09930010 |
Aug 15, 2001 |
|
|
|
09550826 |
Apr 18, 2000 |
|
|
|
Current U.S.
Class: |
501/32 ;
257/E23.009; 428/209 |
Current CPC
Class: |
H01L 2924/00 20130101;
H05K 1/0306 20130101; H01L 2924/0002 20130101; H01L 2924/09701
20130101; C04B 35/111 20130101; C03C 14/004 20130101; H01L
2924/0002 20130101; Y10S 428/901 20130101; C03C 8/14 20130101; Y10T
428/24926 20150115; H01L 23/15 20130101; Y10T 428/24917
20150115 |
Class at
Publication: |
501/32 ;
428/209 |
International
Class: |
B32B 015/04; C03C
014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 8, 1999 |
JP |
11-160642 |
Claims
What is claimed is:
1. A composition for a ceramic substrate comprising a mixture of:
powdered borosilicate glass comprising about 5% to 17.5% by weight
of B.sub.2O.sub.3, about 28% to 44% by weight of SiO.sub.2, 0% to
about 20% by weight of Al.sub.2O.sub.3 and about 36% to 50% by
weight of MO, wherein MO is at least one member selected from the
group consisting of CaO, MgO and BaO; and a powdered ceramic; in
which the amount of the powdered borosilicate glass is about 40% to
49% by weight based on the total amount of the composition for a
ceramic substrate, and the amount of the powdered ceramic is about
60% to 51% by weight based on the total amount of the composition
for a ceramic substrate, and the composition after sintering
comprises a precipitated crystal phase comprising alumina and
wollastonite.
2. The composition for a ceramic substrate according to claim 1,
wherein the coefficient of thermal expansion after sintering is
about 6.0 ppm/.degree. C. or more.
3. The composition for a ceramic substrate according to claim 2,
wherein the powdered ceramic comprises powdered alumina.
4. The composition for a ceramic substrate according to claim 3,
wherein the borosilicate glass contains at least one alkali metal
oxide selected from the group consisting of Li.sub.2O, K.sub.2O and
Na.sub.2O in a positive amount of about 5 parts by weight or less
relative to 100 parts by weight of the total of the B.sub.2O.sub.3,
SiO.sub.2, Al.sub.2O.sub.3 and MO.
5. The composition for a ceramic substrate according to claim 4,
wherein the borosilicate glass contains at least one compound
selected from the group consisting of TiO.sub.2, ZrO.sub.2,
Cr.sub.2O.sub.3, CaF.sub.2 and CuO in a positive amount of about 5
parts by weight or less relative to 100 parts by weight of the
total of the B.sub.2O.sub.3, SiO.sub.2, Al.sub.2O.sub.3 and MO.
6. The composition for a ceramic substrate according to claim 5,
wherein the borosilicate glass comprises 6% to 16% by weight of
B.sub.2O.sub.3, 35% to 43% by weight of SiO.sub.2, 5% to 17% by
weight of Al.sub.2O.sub.3 and 37% to 45% by weight of MO, MO
comprises CaO, the amount of the powdered borosilicate glass is 41%
to 48% by weight, the amount of alkali metal oxide is 1 to 3 parts
by weight and the amount of said at least one compound selected
from the group consisting of TiO.sub.2, ZrO.sub.2, Cr.sub.2O.sub.3,
CaF.sub.2 and CuO is 0.25 to 1 part by weight.
7. The composition for a ceramic substrate according to claim 6,
wherein the coefficient of thermal expansion after sintering is at
least 6.3 ppm/.degree. C.
8. The composition for a ceramic substrate according to claim 1,
wherein the borosilicate glass contains at least one compound
selected from the group consisting of TiO.sub.2, ZrO.sub.2,
Cr.sub.2O.sub.3, CaF.sub.2 and CuO in a positive amount of about 5
parts by weight or less relative to 100 parts by weight of the
total of the B.sub.2O.sub.3, SiO.sub.2, Al.sub.2O.sub.3 and MO.
9. The composition for a ceramic substrate according to claim 2,
wherein the borosilicate glass contains at least one alkali metal
oxide selected from the group consisting of Li.sub.2O, K.sub.2O and
Na.sub.2O in a positive amount of about 5 parts by weight or less
relative to 100 parts by weight of the total of the B.sub.2O.sub.3,
SiO.sub.2, Al.sub.2O.sub.3 and MO.
10. The composition for a ceramic substrate according to claim 2,
wherein the borosilicate glass contains at least one compound
selected from the group consisting of TiO.sub.2, ZrO.sub.2,
Cr.sub.2O.sub.3, CaF.sub.2 and CuO in a positive amount of about 5
parts by weight or less relative to 100 parts by weight of the
total of the B.sub.2O.sub.3, SiO.sub.2, Al.sub.2O.sub.3 and MO.
11. The composition for a ceramic substrate according to claim 1,
wherein the borosilicate glass contains at least one alkali metal
oxide selected from the group consisting of Li.sub.2O, K.sub.2O and
Na.sub.2O in a positive amount of about 5 parts by weight or less
relative to 100 parts by weight of the total of the B.sub.2O.sub.3,
SiO.sub.2, Al.sub.2O.sub.3 and MO.
12. The composition for a ceramic substrate according to claim 1,
wherein the powdered ceramic comprises powdered alumina.
13. The composition for a ceramic substrate according to claim 1,
containing SiO.sub.2 and CaO in relative amounts such that
wollastonite is precipitated after sintering.
14. The composition for a ceramic substrate according to claim 1,
wherein the borosilicate glass is lead-free.
15. The composition for a ceramic substrate according to claim 1,
wherein the borosilicate glass is zinc free.
16. The composition for a ceramic substrate according to claim 1 in
the form of a ceramic green sheet.
17. A ceramic circuit component comprising: a substrate comprising
a molded and sintered composition for a ceramic substrate according
to claim 1; and a conductive circuit in association with the
substrate.
18. The ceramic circuit component according to claim 17, wherein
the conductive circuit comprises at least one metal selected from
the group consisting of Ag, Au and Cu.
19. A ceramic circuit component comprising: a substrate comprising
a molded and sintered composition for a ceramic substrate according
to claim 2; and a conductive circuit in association with the
substrate.
20. The ceramic circuit component according to claim 19, wherein
the conductive circuit comprises at least one metal selected from
the group consisting of Ag, Au and Cu.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional of U.S. patent application Ser. No.
09/550,826, filed Apr. 18, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a composition for a ceramic
substrate and a ceramic circuit component, and more particularly to
a composition for a ceramic substrate which can be sintered at a
temperature as low as 1,000.degree. C. or less, and a ceramic
circuit component, such as a multilayered integrated circuit
component and a thick-film hybrid circuit component, which is
fabricated using the composition for the ceramic substrate.
[0004] 2. Description of the Related Art
[0005] Currently, alumina substrates are predominantly used as
ceramic substrates. In order to obtain an alumina substrate, firing
must be performed at a temperature as high as approximately
1,600.degree. C., and thereby, for example, when a multilayered
circuit component is fabricated using the alumina substrate, a
metal having a high melting point must be used for internal
conductors. However, the metal having a high melting point
generally has a high resistance and is thus unsuitable for
conductors used for multilayered circuit components in which higher
frequencies and higher speeds are increasingly in demand.
[0006] Accordingly, glass-ceramic substrates having a firing
temperature of 1,000.degree. C. or less, which enable use of metals
having a low resistance as internal conductors, such as Au, Ag,
Ag--Pd, Ag--Pt and Cu, have been receiving attention and various
types of glass-ceramic substrates have been developed.
[0007] For example, Japanese Examined Patent Publication No.
3-53269 discloses a low-temperature sinterable ceramic substrate
which is obtained by mixing 50% to 64% by weight of powdered glass
and 50% to 35% by weight of powdered Al.sub.2O.sub.3, followed by
sintering at 800 to 1,000.degree. C.
[0008] However, with respect to such a substrate in which glass is
loaded at the rate of 50% or more, the proportion of crystalline
substances in the sintered substrate is decreased, and thus the
dielectric loss of the substrate may be increased or it may be
difficult to obtain high mechanical strength, which is
disadvantageous. Additionally, when a thick-film electrode and a
thick-film resistor are baked on the surface of the sintered
substrate, the substrate easily deforms under the influence of the
remaining glass, which is also disadvantageous.
[0009] As a solution to the problems described above, the
composition of the powdered glass as a starting material may be
arranged so as to be easily crystallized after sintering, thus
increasing the proportion of crystalline substances in the sintered
substrate. However, with a substrate having a large proportion of
glass in the starting material, such as with a glass load of 50% or
more, strain in the substrate caused by the crystallization of
glass during firing is influential, and deformation, such as
warpage and cracking, easily occurs in the sintered substrate,
which is disadvantageous.
[0010] Japanese Examined Patent Publication No. 4-42349 discloses a
low-temperature sinterable ceramic composition in which 40% to 50%
by weight of powdered glass, composed of 10% to 55% by weight of MO
(where M is at least one of Ca and Mg), 0% to 30% by weight of
Al.sub.2O.sub.3, 45% to 70% by weight of SiO.sub.2, and 0% to 30%
by weight of B.sub.2O.sub.3, and 60% to 50% by weight of powdered
Al.sub.2O.sub.3 are mixed and fired at 1,100.degree. C. or less.
The above patent publication also discloses that by increasing the
proportion of the powdered Al.sub.2O.sub.3 in the starting
material, a transverse strength of 2,600 to 3,200 kgf/cm.sup.2 (255
to 314 MPa) can be obtained. However, such transverse strength is
lower than the transverse strength (approximately 350 MPa) of the
alumina substrate which is used as a circuit substrate, and higher
strength is desired.
[0011] The substrate disclosed in the same patent publication has a
coefficient of thermal expansion in the range from 4.0 to 5.7
ppm/.degree. C. It has been believed that a substrate having a low
coefficient of thermal expansion is preferable on the assumption
that a silicon chip (IC) having a coefficient of thermal expansion
of 3.5 ppm/.degree. C. is directly mounted on the substrate.
However, due to the development of a mounting method in which
stress is relieved using a cushioning material such as an
underfilling, a mismatch in the coefficient of thermal expansion
between the ceramic substrate and the silicon chip does not greatly
cause a problem. In addition, the size of the silicon chip has not
increased as has been expected.
[0012] Under the circumstances where the ceramic substrate is
joined to a larger resin substrate as a motherboard, a mismatch in
the coefficient of thermal expansion between the ceramic substrate
and the resin substrate is rather influential. For example, a
typical glass epoxy (FR-4) has a coefficient of thermal expansion
of 14 to 16 ppm/.degree. C., and an epoxy reinforced with Aramid
fibers has a coefficient of thermal expansion of approximately 8
ppm/.degree. C. If a degree of mismatch in the coefficient of
thermal expansion between the ceramic substrate and the resin
substrate is increased, the reliability of the connection between
the two substrates is lost, which is disadvantageous.
SUMMARY OF THE PRESENT INVENTION
[0013] To overcome the above described problems, preferred
embodiments of the present invention provide a composition for a
ceramic substrate and a ceramic circuit component fabricated using
the same, in which the problems described above can be solved.
[0014] More specifically, in accordance with the preferred
embodiments of the present invention, a composition for a ceramic
substrate used for electronic circuits with a firing temperature of
1,000.degree. C. or less is provided, thus enabling metals having a
low resistance, such as Au, Ag, Ag--Pd, Ag--Pt and Cu, to be used
as internal conductors. In a ceramic substrate obtained by firing
the composition, it is possible to achieve a transverse strength of
300 MPa or more, a Q factor (1 MHZ) of 1,400 or more, and a
coefficient of thermal expansion of 6.0 ppm/.degree. C. or
more.
[0015] One preferred embodiment of the present invention provides a
composition for a ceramic substrate, comprising a mixture of:
powdered borosilicate-based glass comprising about 5% to 17.5% by
weight of B.sub.2O.sub.3, about 28% to 44% by weight of SiO.sub.2,
0% to about 20% by weight of Al.sub.2O.sub.3, and about 36% to 50%
by weight of MO (where MO is at least one selected from the group
consisting of CaO, MgO and BaO); and a powdered ceramic; in which
the amount of the powdered borosilicate-based glass is about 40% to
49% by weight based on the total amount of the composition for a
ceramic substrate, and the amount of the powdered ceramic is about
60% to 51% by weight based on the total amount of the composition
for a ceramic substrate.
[0016] Preferably, the composition for the ceramic substrate has a
coefficient of thermal expansion of about 6.0 ppm/.degree. C. or
more after sintering.
[0017] Preferably, the powdered ceramic contains powdered
alumina.
[0018] The borosilicate-based glass may contain at least one alkali
metal oxide selected from the group consisting of Li.sub.2O,
K.sub.2O and Na.sub.2O, the amount of the alkali metal oxide being
about 5 parts by weight or less relative to 100 parts by weight of
the total amount of the B.sub.2O.sub.3, SiO.sub.2, Al.sub.2O.sub.3,
and MO.
[0019] The borosilicate-based glass may contain at least one
compound selected from the group consisting of TiO.sub.2,
ZrO.sub.2, Cr.sub.2O.sub.3, CaF.sub.2 and CuO, the amount of the
compound being about 5 parts by weight or less relative to 100
parts by weight of the total amount of the B.sub.2O.sub.3,
SiO.sub.2, Al.sub.2O.sub.3 and MO.
[0020] Another preferred embodiment of the present invention
provides a ceramic circuit component comprising a substrate
obtained by molding and sintering the composition for the ceramic
substrate described above and a conductive circuit provided in
association with the substrate.
[0021] In the ceramic circuit component, the conductive circuit
preferably contains at least one metal selected from the group
consisting of Ag, Au and Cu as a principal ingredient.
[0022] According to the composition for the ceramic substrate of
the present invention as described above, since low-temperature
sintering at 1,000.degree. C. or less is enabled, when a ceramic
circuit component provided with a conductive circuit containing a
metal having a low resistance, such as an Ag-based metal or a
Cu-based metal is fabricated, firing can be performed
simultaneously with the metal for the conductive circuit. In the
ceramic substrate fabricated using the composition, it is possible
to achieve a high mechanical strength, a low dielectric constant, a
low loss and a high coefficient of thermal expansion required for
the substrate. Accordingly, a ceramic circuit component, such as a
multilayered ceramic circuit component, having satisfactory
characteristics and high reliability can be obtained.
[0023] In particular, since it is possible to achieve in accordance
with the composition for the ceramic substrate of the present
invention, a coefficient of thermal expansion of about 6.0
ppm/.degree. C. or more, satisfactory matching in the coefficient
of thermal expansion with a motherboard composed of, for example,
an epoxy resin, is obtained, resulting in high connection
reliability.
[0024] In accordance with the composition for the ceramic substrate
of the present invention, when the borosilicate-based glass
contains at least one alkali metal oxide selected from the group
consisting of Li.sub.2O, K.sub.2O and Na.sub.2O with an amount of
about 5 parts by weight or less relative to 100 parts by weight of
the total of B.sub.2O.sub.3, SiO.sub.2, Al.sub.2O.sub.3 and MO, the
softening and flow properties of the glass are accelerated, and
even if the glass amount is reduced in the composition for the
ceramic substrate, a relatively low sintering temperature can be
maintained.
[0025] In accordance with the composition for the ceramic substrate
of the present invention, when the borosilicate-based glass
contains at least one compound selected from the group consisting
of TiO.sub.2, ZrO.sub.2, Cr.sub.2O.sub.3, CaF.sub.2 and CuO with an
amount of about 5 parts by weight or less relative to 100 parts by
weight of the total of B.sub.2O.sub.3, SiO.sub.2, Al.sub.2O.sub.3
and MO, the crystallization of the glass is accelerated, and it is
possible to further improve the high mechanical strength and the
low loss of the resultant ceramic substrate.
[0026] Other features and advantages of the present invention will
become apparent from the following description of the invention
which refers to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0027] FIG. 1 is a sectional view of a multilayered ceramic circuit
component 1 in accordance with an embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] The present invention is characterized in that, with respect
to a composition for a ceramic substrate composed of a mixture of
powdered borosilicate-based glass and a powdered ceramic, such as
powdered alumina, which can be fired at low temperatures, by using
a powdered borosilicate-based glass having a composition which is
easily crystallized after sintering as a sintering additive, and by
setting the glass amount lower than the ceramic amount, the
proportion of crystalline substances in the sintered ceramic
substrate is increased, and a low-temperature sinterable ceramic
substrate having a high mechanical strength, a coefficient of
thermal expansion as high as about 6.0 ppm/.degree. C. or more, and
a low loss can be obtained.
[0029] As described above, the crystallization of glass during
firing causes strain in the ceramic substrate and deformation may
occur in the sintered ceramic substrate. However, since the amount
of glass used in the present invention is about 49% by weight or
less, which is smaller than the amount of the ceramic, the
deformation of the ceramic substrate resulting from the
crystallization of the glass during firing can be advantageously
suppressed.
[0030] The glass functions as a sintering additive for sintering
the ceramic substrate at 1,000.degree. C. or less due to softening
and viscous flow in the firing process. In order to secure the
function as the sintering additive, the amount of glass added must
be about 40% by weight or more.
[0031] As described above, a crystal phase of wollastonite,
anorthite, and the like is easily precipitated from the glass
component which is in the softened and viscous flow state, thus
enabling the sintered ceramic substrate to have a high mechanical
strength and a low loss.
[0032] The glass is composed of B.sub.2O.sub.3 and SiO.sub.2 as
glass network-forming oxides, MO as a glass network-modifying oxide
(where MO is at least one oxide selected from the group consisting
of CaO, MgO and BaO), and Al.sub.2O.sub.3 as a glass network
intermediate oxide which exhibits the network-forming capacity in
collaboration with the network-modifying oxide. The proportion of
the oxides is adjusted so that the glass functions as the sintering
additive for sintering the ceramic substrate at 1,000.degree. C. or
less and the crystal phase is easily precipitated in the sintering
process.
[0033] Of the B.sub.2O.sub.3 and SiO.sub.2 glass network-forming
oxides, B.sub.2O.sub.3 is an oxide for reducing the softening
temperature and accelerating viscous flow, and the amount thereof
is selected at about 5% to 17.5% by weight. If the amount is less
than about 5% by weight, the softening and flow properties of the
glass are degraded. If the amount is more than about 17.5% by
weight, the water resistance of the glass becomes insufficient, and
the properties of the ceramic substrate may be changed when used in
a high temperature and high humidity environment, and also the Q
factor of the glass itself is decreased, thus decreasing the Q
factor of the resultant ceramic substrate.
[0034] In the glass network-forming oxides, the SiO.sub.2 amount is
selected at about 28% to 44% by weight. If the SiO.sub.2 amount is
less than about 28% by weight, the dielectric constant of the
remaining glass itself is increased and a ceramic substrate having
a low dielectric constant cannot be obtained. On the other hand, if
the amount is more than about 44% by weight, the softening and flow
properties of the glass are degraded and thus the ceramic substrate
cannot be sintered at 1,000.degree. C. or less. The crystallization
of the glass is also inhibited, and thus characteristics such as a
high mechanical strength and a low loss cannot be achieved, and the
coefficient of thermal expansion of the ceramic substrate is
decreased.
[0035] The amount of Al.sub.2O.sub.3 as the glass network
intermediate oxide is 0% to about 20% by weight. The
Al.sub.2O.sub.3 acts as a glass intermediate oxide and stabilizes
the glass structure. If the Al.sub.2O.sub.3 amount exceeds about
20% by weight, the softening and flow properties of the glass are
degraded and the ceramic substrate cannot be sintered at
1,000.degree. C. or less. The crystallization of the glass is also
inhibited, and thus characteristics such as a high mechanical
strength and a low loss cannot be achieved.
[0036] MO as the glass network-modifying oxide is a component for
accelerating the softening and flow properties of the glass and the
amount thereof is selected at about 36% to 50% by weight. If the MO
amount is less than about 36% by weight, the softening and flow
properties of the glass are degraded and the coefficient of thermal
expansion of the resultant ceramic substrate is decreased. On the
other hand, if the MO amount exceeds about 50% by weight, the glass
structure becomes unstable, and a glass of stable quality cannot be
obtained.
[0037] In the production of the glass having the composition
described above, in order to further accelerate the softening and
flow properties, at least one alkali metal oxide selected from the
group consisting of Li.sub.2O, K.sub.2O and Na.sub.2O may be
incorporated with an amount of about 5 parts by weight or less
relative to 100 parts by weight of the total of B.sub.2O.sub.3,
SiO.sub.2, Al.sub.2O.sub.3 and MO. If the amount of the alkali
metal oxide exceeds about 5 parts by weight, the electrical
insulating properties of the glass are degraded, the electrical
insulating properties of the sintered ceramic substrate are
degraded, and the coefficient of thermal expansion of the ceramic
substrate is also decreased.
[0038] In order to further increase the high mechanical strength
and the low loss of the resultant ceramic substrate by accelerating
the crystallization of the glass in the firing process, at least
one compound selected from the group consisting of TiO.sub.2,
ZrO.sub.2, Cr.sub.2O.sub.3, CaF.sub.2 and CuO may be incorporated
with an amount of about 5 parts by weight or less relative to 100
parts by weight of the total of B.sub.2O.sub.3, SiO.sub.2,
Al.sub.2O.sub.3 and MO. If the amount of the compound exceeds 5
parts by weight, the sintered ceramic substrate has an excessively
high dielectric constant since the dielectric constant of the glass
is increased.
[0039] The composition for the ceramic substrate described above is
advantageously used for producing a ceramic circuit component
provided with a substrate obtained by forming and firing the
composition and a conductive circuit formed in relation to the
substrate.
[0040] FIG. 1 is a sectional view which schematically shows a
multilayered ceramic circuit component 1, which is an example of
the ceramic circuit component described above, in accordance with
an embodiment of the present invention. In brief, the multilayered
ceramic circuit component 1 includes a ceramic substrate 2 and a
conductive circuit 3 which is formed in and/or on the surface of
the ceramic substrate 2.
[0041] The ceramic substrate 2 is fabricated by firing a ceramic
green compact obtained by laminating a plurality of green sheets
containing the composition for the ceramic substrate described
above, and includes a plurality of ceramic layers 4 obtained by
firing the plurality of green sheets, respectively.
[0042] The conductive circuit 3 is formed, for example, by firing a
conductive paste containing a conductive component comprising at
least one metal selected from the group consisting of Ag, Au and Cu
as a principal ingredient simultaneously with the ceramic green
compact. The conductive circuit 3 is provided with, for example,
external conductors 5, 6 and 7 which are formed on the surface of
the ceramic substrate 2, and is provided with, for example,
internal conductors 8, 9, 10, 11 and 12 which are formed in the
ceramic substrate 2, and is also provided with via-hole joints 13,
14, 15, 16, 17, 18 and 19.
[0043] The internal conductors 8 and 9 are opposed to each other
with a specific ceramic layer 4 therebetween to constitute a
capacitor section 20. The via-hole joints 16 to 19 and the internal
conductors 10 to 12 are alternately connected to each other to
constitute an inductor section 21.
EXAMPLES
[0044] Compositions for ceramic substrates in the present invention
will now be described in detail based on examples.
[0045] Table 1 shows ingredients of the compositions for ceramic
substrates produced in the examples.
1 TABLE 1 Glass Composition Glass Ceramic MO Al.sub.2O.sub.3
B.sub.2O.sub.3 SiO.sub.2 Others Amount Amount Sample (% by weight)
(% by (% by (% by (parts by (% by (% by No. CaO MgO BaO weight)
weight) weight) weight) weight) Type weight) 1 36 0 0 16 6 42 -- 49
Alumina 51 2 45 0 0 13 14 28 -- 46 Alumina 54 3 50 0 0 7 9.5 33.5
-- 45 Alumina 55 4 37 0 0 20 8 35 -- 45 Alumina 55 5 46 0 0 5 7 42
-- 47 Alumina 53 6 46 0 0 5 7 42 -- 44 Alumina 56 7 35 0 5 12 8 40
-- 44 Alumina 56 8 38 0 0 17 5 40 -- 48 Alumina 52 9 40 0 0 8 12 40
-- 42 Alumina 58 10 42 0 0 5.5 10 42.5 -- 48 Alumina 52 11 42 0 0 5
9 44 -- 49 Alumina 51 12 42 0 0 9.5 6 42.5 -- 48 Alumina 52 13 42 0
0 5.5 10 42.5 -- 48 Alumina 42 Forsterite 10 14 45 0 0 5 7 43
TiO.sub.2: 1.0 48 Alumina 52 15 30 10 0 12 8 40 ZrO.sub.2: 1.0 44
Alumina 56 16 40 0 0 9 8 43 Cr.sub.2O.sub.3: 1.0 46 Alumina 54 17
39 6 0 5 7 43 CaF.sub.2: 1.0 46 Alumina 54 18 45 0 0 5 7 43 CuO:
0.5 46 Alumina 54 19 45 0 0 0 17.5 37.5 CuO: 0.25 41 Alumina 59 20
40 0 0 0 16 44 CuO: 0.25 45 Alumina 55 21 40 0 0 9 8 43 CuO: 0.5 48
Alumina 52 22 37 0 0 20 8 35 Li.sub.2O: 1.0 40 Alumina 60 23 37 0 0
20 8 35 K.sub.2O: 3.0 42 Alumina 58 24 37 0 0 20 8 35 Na.sub.2O:
2.0 41 Alumina 59 25 34 0 0 10 12 44 -- 46 Alumina 54 26 52 0 0 8 8
32 -- 44 Alumina 56 27 37 0 0 22 11 30 -- 48 Alumina 52 28 47 0 0
10 3 40 -- 48 Alumina 52 29 38 0 0 11 19 32 -- 44 Alumina 58 30 49
0 0 18 7 26 -- 46 Alumina 54 31 39 0 0 7 8 46 -- 48 Alumina 52 32
35 5 0 5 13 42 -- 38 Alumina 62 33 40 0 0 7 13 40 -- 52 Alumina
48
[0046] First, oxides or carbonates, as starting materials, were
prepared so as to satisfy the glass compositions shown in Table 1.
A mixture was melted in a Pt crucible for one hour at 1,300 to
1,700.degree. C. according to the glass composition. After the melt
was quenched, grinding was performed and powdered glass for each
sample was obtained. Additionally, Table 1 shows, with respect to
MO (CaO, MgO and BaO), Al.sub.2O.sub.3, B.sub.2O.sub.3 and
SiO.sub.2, which were starting materials, the compositional ratios
in units of "% by weight", and with respect to other starting
materials, such as TiO.sub.2, the compositional ratios are shown in
units of "parts by weight" relative to 100 parts by weight of the
total of MO, Al.sub.2O.sub.3, B.sub.2O.sub.3 and SiO.sub.2.
[0047] Next, each powdered glass obtained as described above and a
powdered ceramic, such as powdered alumina, were mixed at a ratio
between the "glass amount" and the "ceramic amount" shown in Table
1, and a solvent, binder and a plasticizer were added thereto,
followed by fully mixing. By employing the doctor blade process,
green sheets were obtained.
[0048] Based on the green sheets for the individual samples
obtained as described above, several forms of specimens were
prepared, and evaluations were conducted with respect to
"transverse strength", "relative dielectric constant
(.epsilon..sub.r)", "Q", "coefficient of thermal expansion", and
"precipitated crystal phase".
2TABLE 2 Firing Temperature Transverse Strength Coefficient of
Thermal Precipitated Sample No. .degree. C. MPa .epsilon..sub.I Q
Expansion (ppm/.degree. C.) Crystal Phase 1 900 330 8.5 1,900 7.8 A
2 860 340 8.8 2,500 8.8 A, W 3 870 330 8.7 3,200 8.3 A, W 4 880 325
8.6 2,800 8.3 A, W 5 820 350 7.2 4,000 7.9 A, W 6 880 335 7.6 4,300
7.6 A, W 7 880 335 8.7 2,000 7.5 A 8 890 340 8.7 1,700 8.2 A 9 990
350 8.6 1,700 7.4 A 10 850 310 7.9 2,900 7.4 A, W 11 860 310 7.8
3,200 7.2 A, W 12 880 320 8.2 1,900 7.9 A, W 13 860 300 7.7 3,200
7.7 A, W, F 14 880 330 7.8 5,000 7.6 A, W 15 890 335 8.8 2,500 6.3
A, W 16 860 320 8.5 2,600 7.5 A, W 17 870 315 8.7 2,700 6.7 A, W 18
880 340 7.8 3,700 7.5 A, W 19 890 325 8.4 2,500 6.9 A, W 20 860 315
8.6 2,500 6.0 A, W 21 850 325 8.8 2,600 7.5 A, W 22 880 330 8.7
2,100 8.2 A 23 880 330 8.7 2,100 8.2 A 24 880 330 8.7 1,900 8.2 A
25 1,000 dense sintered compact unobtainable 26 880 250 8.2 1,200
8.5 A, W 27 1,000 dense sintered compact unobtainable 28 1,000
dense sintered compact unobtainable 29 820 300 8.8 1,000 7.4 A 30
880 280 9.1 1,500 8.9 A 31 900 290 7.9 1,700 5.8 A, W 32 1,000
dense sintered compact unobtainable 33 840 280 7.9 2,500 7.1 A
[0049] First, after a predetermined number of green sheets for each
sample were laminated and cut in predetermined sizes, firing was
performed at the firing temperature shown in Table 2, and thus a
sintered compact was obtained. By an abrasive process, the
dimensions thereof were set at 36 mm long, 4 mm wide and 3 mm
thick. With respect to the sintered compact thus obtained for each
sample, the transverse strength (three-point bending) was measured
according to Japanese Industrial Standard (JIS) R1601. The
precipitated crystal phase in the sintered compact was also
identified by X-ray diffraction analysis. In the column of the
precipitated crystal phase in Table 2, "A" represents alumina, "W"
represents wollastonite, and "F" represents forsterite.
[0050] After a predetermined number of green sheets for each sample
were laminated, firing was performed at the firing temperature
shown in Table 2. The resultant sintered compact was cut by a
dicing saw and the dimensions were set at 10 mm long, 3 mm wide and
3 mm thick. With respect to the sintered compact of such size, the
coefficient of thermal expansion at 25.degree. C. to 500.degree. C.
was measured.
[0051] Using the green sheets for each sample, a multilayered
ceramic circuit component 1 as shown in FIG. 1 was fabricated. That
is, holes were made in the green sheets and an Ag-based paste was
filled therein to form via-hole joints 13 to 19, and then the
Ag-based paste was screen-printed to form the external conductors 5
to 7 and the internal conductors 8 to 12 in predetermined patterns.
A predetermined number of the green sheets for forming ceramic
layers 4 were laminated, followed by pressing. Firing was performed
in air at the firing temperature shown in Table 2, and thus the
multilayered ceramic circuit component 1 was obtained.
[0052] By applying a voltage with a frequency of 1 MHZ between the
external conductors 5 and 6 in the multilayered ceramic circuit
component 1, the electrostatic capacity and Q of the capacitor
section 20 were measured, and the relative dielectric constant
(.epsilon..sub.r) was calculated. Table 2 shows the relative
dielectric constant (.epsilon..sub.r) and Q.
[0053] In Tables 1 and 2, Sample Nos. 1 to 24 correspond to
examples which are within the scope of the present invention, and
Sample Nos. 25 to 33 correspond to comparative examples which are
out of the scope of the present invention.
[0054] As is clear from Table 2, in Sample Nos. 1 to 24 according
to the present invention, the transverse strength was as high as
300 to 350 MPa, .epsilon..sub.r was in the range from 7.0 to 8.8, Q
was as large as 1,400 to 5,000, and the coefficient of thermal
expansion was as large as 6.0 or more. Thus, satisfactory
characteristics for the ceramic substrate in the ceramic circuit
component were exhibited.
[0055] In Sample Nos. 22 to 24, in which an alkali metal oxide,
such as Li.sub.2O, K.sub.2O or Na.sub.2O, was incorporated in the
glass, since the softening temperature of the glass was decreased
(in comparison with Sample No. 4 having the same glass composition
apart from the fact that an alkali metal was not incorporated), it
was confirmed that firing could be performed at the same
temperature in spite of the decreased amount of glass.
[0056] In Sample Nos. 12 to 21, in which TiO.sub.2, ZrO.sub.2,
Cr.sub.2O.sub.3, CaF.sub.2 or CuO was incorporated in the glass,
although not shown in Table 2, it was confirmed by X-ray
diffraction analysis that the crystallization had been
accelerated.
[0057] In contrast, in comparative example Sample No. 25, since the
amount of alkaline earth metal, namely, M, in the glass was low, a
dense sintered compact was not obtained when sintered at a
temperature of 1,000.degree. C. or less. In Sample No. 26, since
the M amount in glass was high, the glass became unstable, and even
if the firing temperature was optimized, the density of the
sintered compact was not increased sufficiently, and thus the
transverse strength was as low as 250 MPa.
[0058] In Sample No. 27, a dense sintered compact was not obtained
at a firing temperature of 1,000.degree. C. or less because of the
excessively large amount of Al.sub.2O.sub.3 in the glass.
[0059] In Sample No. 28, a dense sintered compact was not obtained
at a firing temperature of 1,000.degree. C. or less because of the
excessively small amount of B.sub.2O.sub.3 in the glass. In Sample
No. 29, Q was as low as 1,000 because of the excessively large
amount of B.sub.2O.sub.3 in the glass.
[0060] In Sample No. 30, the relative dielectric constant
(.epsilon..sub.r) was as large as 9.1 because of the small amount
of SiO.sub.2 in the glass. In Sample No. 31, having an excessively
large amount of SiO.sub.2 in the glass, the coefficient of thermal
expansion was as low as 5.8.
[0061] Because of the small amount of glass added in Sample No. 32,
sintering ended in failure at a firing temperature of 1,000.degree.
C. or less. In Sample No. 33, the transverse strength was as low as
280 Mpa because of the excessively large amount of glass added.
[0062] While the invention has been particularly shown and
described with reference to preferred embodiments thereof, it will
be understood by those skilled in the art that the forgoing and
other changes in form and details may be made therein without
departing from the spirit of the invention.
* * * * *